1. Area of the Art
The present invention relates to a semiconductor device and a method for manufacturing thereof, and more particularly, to a semiconductor device that is capable of miniaturizing devices and has a contact structure using wiring material such as aluminum, and a method for manufacturing the semiconductor device.
2. Description of the Related Art
Semiconductors, such as LSIs, require openings such as contact holes of a greater aspect ratio for higher element miniaturization, higher density integration and increased multiple layers. Many have tried to use aluminum and aluminum alloys that are useful wiring material to fill in contact holes. However, it is difficult to fill such contact holes with wiring material, and therefore it has been an important technical object to overcome, in recent years.
It is an object of an embodiment of the present invention to provide a method for manufacturing a semiconductor device that fills contact holes with conductive material such as aluminum or an aluminum alloy, such that the generation of whiskers in the surface of the conductive material is prevented.
In one or more embodiments of the invention, a semiconductor device is manufactured by the process of forming an opening such as a contact hole in an interlayer dielectric film formed on a semiconductor substrate having a device element. A film formed from conductive material such as aluminum or an alloy having aluminum as a main component is formed on the interlayer dielectric film and the opening. The film is then gradually cooled.
In one or more embodiments of the invention, a semiconductor device is manufactured by the process of forming an opening such as a contact hole in an interlayer dielectric film formed on a semiconductor substrate having an element. A first film formed from conductive material such as aluminum or an alloy having aluminum as a main component is formed on the interlayer dielectric film and the opening at relatively low temperatures. A second film formed from conductive material such as aluminum or an alloy having aluminum as a main component is formed on the first film at temperatures higher than the film formation temperature for forming the first film. The second film is then gradually cooled.
A method for manufacturing a semiconductor device in accordance with one or more embodiments of the invention comprises the steps of forming an opening such as a contact hole in an interlayer dielectric film formed on a semiconductor substrate having an element, forming a conductive coating film preferably formed from aluminum or an alloy having aluminum as a main component on the interlayer dielectric film and the opening, and gradually cooling the coating film.
In one or more embodiments of the invention, when the coating film is gradually cooled, thermal stresses generated in the film are alleviated, and generation of whiskers in the surface of the film is prevented. In one or more embodiments, the coating film may include multiple layers. For example, a first coating film acting as an intermediate layer made of conductive material such as aluminum or an aluminum alloy may be formed at lower temperatures over the interlayer dielectric film first (e.g., temperatures of 200xc2x0 C. or lower, and more preferably about 30xe2x80x94about 100xc2x0 C.). Further, a second film acting as another coating layer made of conductive material such as aluminum or an aluminum alloy may be formed over the first film at higher temperatures (e.g. temperatures of 300xc2x0 C. or higher and more preferably about 350xe2x80x94about 450xc2x0 C.).
Formation of a first coating layer over the intermediate layer under the above-described temperature conditions suppresses the gasification of gas components contained in the interlayer dielectric film and the intermediate layer, and prevents the intermediate layer from lowering its wettability that may be caused by gases discharged outside from the intermediate layer. As a result, the first coating layer can be optimally adhered to the intermediate layer, and therefore film formation is conducted with good step coverage.
The presence of the first coating film suppresses generation of gases from the interlayer dielectric film and the intermediate layer which are provided below the first coating film, even when the temperature of the substrate rises. As a result, the second coating film can be formed, at relatively high temperatures (e.g., 300xc2x0 or higher) in which aluminum alloys can flow and diffuse. As a result, openings such as contact holes formed in the interlayer dielectric film can be filled in with good step coverage and without generating voids. In one or more embodiments of the invention, the stated manufacturing method is successfully applicable to very fine contact holes (e.g., holes of 0.2 xcexcm diameter).
Further, in one or more embodiments of the invention, the coating films are formed by a sputtering method. In a preferred embodiment, the coating films are formed continuously in the same chamber. When the coating films are successively formed in the same chamber, the temperature of the substrate and the chamber atmosphere are readily and accurately controlled so that inconveniences such as formation of an oxide layer on the first coating film are avoided.
In one or more embodiments of the invention, any gasification component contained in the interlayer dielectric film is removed by performing heat treatment at substrate temperatures (e.g., 300xc2x0 C. to 550xc2x0 C.) preferably under reduced pressure. The removal of gasification components (degasification) may preferably be conducted after the formation of the opening in the interlayer dielectric film. In the present invention, the term xe2x80x9cgasification componentsxe2x80x9d refers to gas components (e.g., water, hydrogen, oxygen or nitrogen) generated from deposited layers, such as the interlayer dielectric films and the intermediate layers under reduced pressure and at substrate temperatures. By performing the degasification, generation gases that may be contained in the interlayer dielectric film are suppressed during the formation of the second coating film at relatively high temperatures. Accordingly, by removing gasifying components contained in the interlayer dielectric film, the intermediate layers are securely prevented from lowering their wettability and from developing voids that may be caused by the presence of such gases between the intermediate layers and the coating film that covers those layers.
In one or more embodiments of the invention, gases discharged from the interlayer dielectric film are absorbed by the intermediate layers, but not the coating layers in the contact holes. As a result, contact sections coated with low resistance conductive films with good coverage are formed in the contact holes.
In one or more embodiments of the invention, the substrate temperature is lowered before the intermediate coating film is formed. In some embodiments the forming of the coating film and the cooling of the substrate are continuously performed in the same apparatus having a plurality of chambers that are maintained under a reduced pressure state. This structure reduces the number of steps for transporting and mounting wafers. Accordingly, the process is simplified and pollution of substrates is prevented.
In one or more embodiments of the invention, after gradually cooling the coated films (i.e., the intermediate film and the coating layer formed over the intermediate film), a third film is formed on the above-described films at temperatures ranging from about the normal temperature to about 100xc2x0 C. The formation of the third film, in one or more embodiments, is conducted by a sputtering method. In other embodiments, the gradual cooling of the coating films and forming said third film is continuously performed in the same chamber. This structure reduces the number of steps for transporting and mounting wafers. Accordingly, the process is simplified and pollution of substrates is prevented.
Other features and advantages of the invention will be apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, various features of embodiments of the invention.